String.Format Method

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Replaces each format item in a specified string with the text equivalent of a corresponding object's value.

This member is overloaded. For complete information about this member, including syntax, usage, and examples, click a name in the overload list.

Overload List

  Name Description
Public methodStatic memberSupported by Silverlight for Windows PhoneSupported by Xbox 360 Format(String, Object) Replaces one or more format items in a specified string with the string representation of a specified object.
Public methodStatic memberSupported by Silverlight for Windows PhoneSupported by Xbox 360 Format(String, array<Object[]) Replaces the format item in a specified string with the string representation of a corresponding object in a specified array.
Public methodStatic memberSupported by Silverlight for Windows PhoneSupported by Xbox 360 Format(IFormatProvider, String, array<Object[]) Replaces the format item in a specified string with the text equivalent of the value of a corresponding object in a specified array. A specified parameter supplies culture-specific formatting information.
Public methodStatic memberSupported by Silverlight for Windows PhoneSupported by Xbox 360 Format(String, Object, Object) Replaces the format item in a specified string with the string representations of two specified objects.
Public methodStatic memberSupported by Silverlight for Windows PhoneSupported by Xbox 360 Format(String, Object, Object, Object) Replaces the format items in a specified string with the string representation of three specified objects.

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Remarks

Each overload of the Format method uses the composite formatting feature to include zero-based indexed placeholders, called format items, in a composite format string. At run time, each format item is replaced with the string representation of the corresponding argument in a parameter list. If the value of the argument is nulla null reference (Nothing in Visual Basic), it is replaced with String.Empty. For example, the following call to the Format method includes a format string with three format items, {0}, {1}, and {2}, and an argument list with three items.

Dim dat As Date = #1/17/2012 9:30AM# 
Dim city As String = "Chicago"
Dim temp As Integer = -16
Dim output As String = String.Format("At {0} in {1}, the temperature was {2} degrees.",
                                     dat, city, temp)
outputBlock.Text += output
' The example displays the following output:
'    At 1/17/2012 9:30:00 AM in Chicago, the temperature was -16 degrees.   
DateTime dat = new DateTime(2012, 1, 17, 9, 30, 0); 
string city = "Chicago";
int temp = -16;
string output = String.Format("At {0} in {1}, the temperature was {2} degrees.",
                              dat, city, temp);
inputBlock.Text += output;
// The example displays the following output:
//    At 1/17/2012 9:30:00 AM in Chicago, the temperature was -16 degrees.   

A format item has the following syntax:

**{index[,**alignment][ **:**formatString] }

Brackets denote optional elements. The opening and closing brackets are required. A format item has the following elements:

The following example illustrates how to use optional elements in format items to produce formatted output.

Module Example
   Public Sub Demo(outputBlock As System.Windows.Controls.TextBlock)
      ' Create array of 5-tuples with population data for three U.S. cities, 1940-1950.
      Dim cities()  = _
          { Tuple.Create("Los Angeles", #1/1/1940#, 1504277, #1/1/1950#, 1970358),
            Tuple.Create("New York", #1/1/1940#, 7454995, #1/1/1950#, 7891957),  
            Tuple.Create("Chicago", #1/1/1940#, 3396808, #1/1/1950#, 3620962),  
            Tuple.Create("Detroit", #1/1/1940#, 1623452, #1/1/1950#, 1849568) }

      ' Display header
      Dim header As String = String.Format("{0,-12}{1,8}{2,12}{1,8}{2,12}{3,14}",
                                           "City", "Year", "Population", "Change (%)")
      outputBlock.Text += header + vbCrLf + vbCrLf

      Dim output As String      
      For Each city In cities
         output = String.Format("{0,-12}{1,8:yyyy}{2,12:N0}{3,8:yyyy}{4,12:N0}{5,14:P1}",
                                city.Item1, city.Item2, city.Item3, city.Item4, city.Item5,
                                (city.Item5 - city.Item3)/city.Item3)
         outputBlock.Text += output + vbCrLf
      Next
   End Sub
End Module
' The example displays the following output:
'    City            Year  Population    Year  Population    Change (%)
'    
'    Los Angeles     1940   1,504,277    1950   1,970,358        31.0 %
'    New York        1940   7,454,995    1950   7,891,957         5.9 %
'    Chicago         1940   3,396,808    1950   3,620,962         6.6 %
'    Detroit         1940   1,623,452    1950   1,849,568        13.9 %
using System;

public class Example
{
   public static void Demo(System.Windows.Controls.TextBlock outputBlock)
   {
      // Create array of 5-tuples with population data for three U.S. cities, 1940-1950.
      Tuple<string, DateTime, int, DateTime, int>[] cities = 
          { Tuple.Create("Los Angeles", new DateTime(1940, 1, 1), 1504277, 
                         new DateTime(1950, 1, 1), 1970358),
            Tuple.Create("New York", new DateTime(1940, 1, 1), 7454995, 
                         new DateTime(1950, 1, 1), 7891957),  
            Tuple.Create("Chicago", new DateTime(1940, 1, 1), 3396808, 
                         new DateTime(1950, 1, 1), 3620962),  
            Tuple.Create("Detroit", new DateTime(1940, 1, 1), 1623452, 
                         new DateTime(1950, 1, 1), 1849568) };

      // Display header
      string header = String.Format("{0,-12}{1,8}{2,12}{1,8}{2,12}{3,14}\n",
                                    "City", "Year", "Population", "Change (%)");
      outputBlock.Text += header + Environment.Newline;
      string output;      
      foreach (var city in cities) {
         output = String.Format("{0,-12}{1,8:yyyy}{2,12:N0}{3,8:yyyy}{4,12:N0}{5,14:P1}",
                                city.Item1, city.Item2, city.Item3, city.Item4, city.Item5,
                                (city.Item5 - city.Item3)/city.Item3 * 1.0);
         outputBlock.Text += output + Environment.Newline;
      }
   }
}
// The example displays the following output:
//    City            Year  Population    Year  Population    Change (%)
//    
//    Los Angeles     1940   1,504,277    1950   1,970,358        31.0 %
//    New York        1940   7,454,995    1950   7,891,957         5.9 %
//    Chicago         1940   3,396,808    1950   3,620,962         6.6 %
//    Detroit         1940   1,623,452    1950   1,849,568        13.9 %